In recent years, in the field of the high intensity discharge lamp lighting device, a high intensity discharge lamp control system with such a high function that moves, for example, a spotlight and the like by an actuator has been examined while the conventional apparatus only lights a lamp in response to ON/OFF of a power switch.
In particular, in the field of the vehicle headlamp, a vehicle that mounts thereon a high intensity discharge lamp (hereinafter, referred to as an HID lamp) as a load has been widespread, and a vehicle headlamp lighting device (HLB: head light ballast) that lights the HID lamp has also been being widespread. Moreover, in recent years, a vehicle that mounts thereon a control ECU (electronic control unit) that drives the headlamp or an auxiliary lamp up and down and left and right in response to vehicle information such as a steering angle and a vehicle speed has also been started to be widespread.
Heretofore, the lighting device of the vehicle HID lamp has started to operate by ON/OFF of the power switch located close to the hand of a driver, and lights the HID lamp by using a square wave after the HID lamp is started. In this event, as described in Japanese Patent Laid-Open Publication No. 2004-355833, since a voltage and current of the lamp are unstable at the time when a polarity of the square wave is inverted and for a predetermined time, a period (sample hold time) while the voltage and the current are not being detected and a control for constantly maintaining the power is not being performed is provided. Specifically, during this period, a load on a microcomputer that performs the control for constantly maintaining the power is small.
Moreover, in recent years, as described in Japanese Patent Laid-Open Publication No. 2002-178829 and Japanese Patent Laid-Open Publication No. 2003-159989, there has been a technology in which, separately from the lighting device of the HID lamp, an ECU that starts to operate by operating an ignition switch or an accessory switch (alternatively, always operates by direct connection to a battery) and drives the headlamp or the auxiliary lamp is provided in the vicinity of the headlamp, in a vehicle cabin or in the like. The drive of the headlamp or the auxiliary lamp affects visibility at night, and accordingly, a control for a motor that drives the headlamp or the auxiliary lamp is performed extremely complicatedly. Microcomputers are used individually for the lighting device and the ECU in order to realize the above-described control.
Configurations of these components are shown in FIG. 27 and FIG. 28. In these diagrams, reference symbols M1 and M3 denote optical axis varying motors of a left lamp body, reference symbols M2 and M4 denote optical axis varying motors of a right lamp body, reference symbol La1 denotes an HID lamp of the left lamp body, and reference symbol La2 denotes an HID lamp of the right lamp body. Reference symbols HLB1 and HLB2 denote headlamp lighting devices, and upon being supplied with power Es by a switch located close to the hand of the driver, the headlamp lighting devices HLB1 and HLB 2 light the lamps La1 and La2. Reference symbols W1, W2, W3 and W3 denote bundles of wire harnesses for driving the respective motors.
In a first conventional example of FIG. 27, an ECU in the vehicle cabin obtains the information on the vehicle speed and the steering angle by a vehicle network (CAN communication line) represented, for example, by CAN (controlled area network) and the like. The ECU drives the headlamps or the auxiliary lamps up and down or left and right based on the information on the vehicle speed and the steering angle. With regard to the lighting of the headlamps, the HID lamps are lighted by the switch located close to the hand of the driver.
In a second conventional example of FIG. 28, an ECU in the vehicle cabin obtains the information on the vehicle speed and the steering angle by a vehicle network. The ECU arithmetically operates target positions for driving the headlamps or the auxiliary lamps, target angles of optical axes, and the like based on the information on the vehicle speed and the steering angle, and communicates with individual ECU1 and ECU2 on the left and right lamp body sides through a local communication line (for example, LIN (local interconnect network)) different from the above-described network. The individual ECU1 and ECU2 on the left and right lamp body sides drive the headlamps or the auxiliary lamps up and down or left and right based on such information thus obtained. In a similar way to the first conventional example, with regard to the lighting of the headlamps, the HID lamps are lighted by the switch located close to the hand of the driver.
Note that, in Japanese Patent Laid-Open Publication No. 2006-7987, a configuration is disclosed, in which the lighting device of the HID lamp and the ECU that drives the headlamp or the auxiliary lamp are integrated with each other.
However, in the configurations of FIG. 27 and FIG. 28, the lighting devices of the HID lamps and the controlling microcomputers for the respective ECUs become necessary. Accordingly, in each of the configurations, total cost of a front module is increased. In this connection, it is considered to reduce the total cost by integrating the lighting devices and the ECU with each other in terms of control. However, the lighting device of each HID lamp performs a fine feedback control for the lamp power so as not to give flickering of light to the driver. Meanwhile, each ECU that varies a light distribution in response to the steering angle is required to perform a communication control, acquisition of vehicle information by A/D conversion, and a smooth motor control so as to give more safe and comfortable visibility to the driver. Both of the power feedback control and the motor control largely affect the visibility of the driver, real time performance is required for each thereof, and a major part of the performance of each microcomputer is occupied for controlling these factors. Therefore, it has been extremely difficult for one microcomputer to realize the feedback control for the lamp power and the control for the motor.
Moreover, though such a vehicle headlamp control apparatus is shown here, a similar problem is inherent also in the case of realizing, by one microcomputer, a lighting control for an HID lamp for common illumination, such as a spotlight and a downlight, and a control for varying a light distribution thereof.
The present invention has been made in consideration for the above-described points. It is an object of the present invention to make it possible to realize, by an inexpensive microcomputer, the lighting control for the discharge lamp, other communication controls, and the smooth drive control for the headlamp or the auxiliary lamp by moving the motor.